Convertible electrode electric furnace installation and method

ABSTRACT

An electric furnace installation in which a simple interchangeability of electrode clamping assemblies is provided to permit electrode melting operation in which single or plural electrodes can be mounted on the basic furnace tower for melting in a crucible means. The interchangeable electrode clamping assemblies are designed for ease of rapid removal from and rapid connection onto an upper carriage of the basic furnace. A lower carriage which helps support and stabilize the crucible can accommodate crucibles for single and for plural electrode melting.

United States Patent [1 1 11 3,709,997 Medovar et al. 451 Jan, 9, 1973 [54] CONVERTIBLE ELECTRODE [56] References Cited ELECTRIC FURNACE INSTALLATION AND METHOD UNITED STATES PATENTS [76] Inventors: Boris lznikvich Medov", Bulvar 3,510,562 5/1970 Frauenstein ..l3/9 ES Lesi Ukrainki, 2, kv. 8; Vlktor Andreevich Popov, ulitsa Andreevgrlmary qr g N fil & K skaya, ll, apt. 2; Jury Fedorovich ttorney-- rauc oan, ea e, res urz Alferov, Bulvar Lepse, 29, kv. 64; Alexey Georgievlcli Bogachenko, [57] ABSTRACT ulitsa Milyutenko, 15/2, apt. 141; An electric furnace installation in which a simple in- Jury Vadimovich Latash, Vozdukterchangeability of electrode clamping assemblies is hoflotsky prosp. 81/2, kv. 14, all of provided to permit electrode melting operation in Kiev, U.S.S.R. which single or plural electrodes can be mounted on the basic furnace tower for melting in a crucible [22] Filed 1970 means. The interchangeable electrode clamping as- [21] App]. No.: 100,709 semblies are designed for ease of rapid removal from and rapid connection onto an upper carriage of the basic furnace. A lower carriage which helps support o u u n e l e u u u a u I n n I e a n u n a a e s e n e n u s n 58 Field of Search ..13/9 ES, 14-1 7 smgle and for plural electmde 58 Claims, 9 Drawing Figures PATENTED JAN 9 I973 SHEET 8 [IF 7' ALEXY "s. BOGACHENKO JURY v. LATASH PATENTEDJM ems 9.709.997

SHEET 3 0F 7 INVENTORS BORIS I. MEDOVAR POPOV LFEROV ALEXY G. BOGACHENKO JURY V. LATASH BY 2% ,wfa/i /ATTORN Y5 PATENTEDJAN 9 ma SHEEI 0F 7 ALEXY s. BOGACHENKQ JURY v. LATASH PATENTED JAN 9 I973 3. 7 09,99 7

SHEET 5 OF 7 INVENTORS BORIS I. MEDOVAR VIKTOR A. POPOV JURY F. ALFEROV ALEXY G BOGAGHENKO JURY v. LATASH ATTORN 5 CONVERTIBLE ELECTRODE ELECTRIC FURNACE INSTALLATION AND METHOD BACKGROUND AND FIELD OF THE INVENTION The present invention relates to an electric furnace installation which can be used in alternative modes, as desired, for melting a single electrode during one time period of operation and melting at least two electrodes simultaneously at another time period. More particularly, the invention relates to a convertible electric furnace installation which is convertible between a single electrode melting mode and a bifilar electrode melting mode.

The previously known electric furnace art, particularly that pertaining to electroslag remelting furnaces, includes furnace installations designed for melting single electrodes as shown by British Pat. No. 1,103,350 published Jan. 6, 1965 and furnace installations for melting multiple electrodes arranged for simultaneously melting as shown by R.K. Hopkins, US. Pat. No. 2,445,670, July 20, 1948 and Belgium Pat. No. 670,299, Jan. 17, 1966. However, the prior art represented by such patents does not disclose a furnace installation which is convertible between two modes, at single electrode melting mode and a bifilar electrode melting mode. Total redesign of the entire structures of the previously known electroslag remelting furnaces would be required in order to provide a convertible melting mode capability and, in those furnaces, such conversion is not practical for commercial operations.

From past experience it appears that a prerequisite for a commercially acceptable convertible furnace installation is to provide basic furnace components that remain unchanged while permitting different numbers of electrodes to be supported by different clamping assemblies. At the same time, the clamping assemblies for different modes must be easily removable from the basic furnace structure with quick conversion and connections of electric power lines for the different modes. The different clamping assemblies must be interchangeable within permissible operating time limits while still being of simple design so as to overly complicate the upper structure of the furnace tower.

In order to be easily convertible between the two different melting modes, the electrode clamping assemblies must be in an exposed position and the components by which the clamping assemblies are mounted on the upper carriage of the electric furnace installation, to enable interchangeability, must consist of only a few key elements. The prior art fails to teach these types of interchangeable clamping assemblies in any furnace installation. Thus, it was not possible to provide a convertible furnace by using the same clamping assemblies as previously employed on different furnaces to provide for a convertible, two melting mode operation.

The commercial significance ofa convertible electric furnace installation resides in the fact that certain ingot configurations can only practically be made in an electroslag remelting furnace by the use of a single electrode; whereas, certain other ingot configurations require the use and simultaneous melting of at least a pair of electrodes. For example, a circular cross-section ingot, particularly in the lower tonnage values, is most efficiently made by using a single, circular cross-section electrode. On the other hand, a slab-shaped ingot from LII which steel plate can be rolled can best be produced by employing two parallel electrodes, referred to herein as a pair of bifilar electrodes. in the past these two operations required two furnace installations, and due to the substantial expense and added operational costs of maintaining two separate furnaces, one for one melting mode and the other for the other melting mode, it is advantageous both from the standpoint of equipment costs and of operating expenses to use a single basic furnace installation together with only a minimum number of elements enabling conversion between a single electrode melting mode and bifilar electrode melting mode. It is clearly apparent that a greater range of ingot shapes can be produced for a lower total cost than the cost involved when separate furnace installations are employed.

SUMMARY OF THE INVENTION The present invention accomplishes the need for a single basic furnace installation capable'of single and bifilar modes of electrode melting operations. It provides a basic furnace tower on which upper and lower carriages are mounted for controlled vertical movement along the tower. The upper carriage serves to mount the interchangeable electrode clamping assemblies, which mechanically support the electrodes relative to the tower. The upper carriage also provides for interchangeably connecting the electrodes in the different operational modes with a source of operating electric current. The electrode(s) are supported with the lower end(s) extending into a cooled crucible assembly which can be moved into and out of position directly under the clamped electrode(s).

For a single electrode melting mode, the electrode clamping assembly includes a pair of tongs with electrode clamping jaws which physically clamp an electrode through the medium of electrode contact shoes which supply electrical power to the electrode. Power mechanism is provided for operating the electrode jaws. They are urged into clamping engagement with the electrode by mechanical linkages which utilize the weight of the upper carriage, electrode clamping means, and the electrode itself to apply the clamping force. This mechanism uses a fluid pressure motor to open the electrode clamping jaws against the force of the weight which urges them closed.

The electrode clamping assembly for a single electrode can be removed from the upper carriage by disconnecting various power links and a single coupling pin between the assembly and the upper carriage. The entire clamping assembly can then be removed, as by an overhead or a stationary crane as desired. The fluid motor is removably attached to the upper carriage, and while it need not be removed it can be easily dismounted, if desired.

When the single electrode clamping assembly is removed it can be replaced by a clamping assembly for bifilar electrodes. The bifilar clamping assembly is hoisted to a position adjacent the upper carriageand a different coupling pin is inserted through the clamping assembly support brackets provided on the upper carriage. During the conversion, the electrical power leads to the electrode clamping assembly which is removed are disconnected and then are reconnected in appropriate arrangement to the other electrode clamping assembly. As described in detail hereinafter, the electrical power lead conversion is made simply and with few disconnection procedures.

The bifilar clamping assembly as disclosed, functions to clamp the electrodes against L-shaped electrode shoes by means of hand operated clamping bolts. The only structural connection between the bifilar clamping assembly and the upper carriage is via the brackets on the assembly and the carriage and the coupling pin. Therefore, to orient the assembly on the carriage the pin reception apertures in the brackets are square and the cross-section of the pin is square to match the bracket apertures. After the electrical power line connections are made, the two electrodes can be positioned in the clamping assembly, and the clamping bolts screwed tight to grip the electrodes and thus support them on the upper carriage. Provision is also made for fastening the cable, pulley and counter-weight system as used in the single electrode mode, to the upper carriage so, the weight of the upper carriage and the two electrodes is counter-balanced by the counterweight located within the furnace tower.

To provide for greatest convenience and most efficient conversion between single and bifilar modes, the weight of the interchanged parts, including the electrodes, positioned upon the upper carriage of the electric furnace installation, should be controlled to be close to the same weight so that additional counterweights do not have to be installed on the main counter-weight assembly located in the furnace tower.

Thus, in accord with the foregoing summary of the invention, a primary object of the present invention is to provide an electric furnace installation in which the basic furnace structure is convertible between a single electrode melting mode and a bifilar electrode melting mode.

Another object of the present invention is to provide for a clamping means for a single electrode which can be quickly and easily installed on the upper carriage of an electric furnace tower and connected with an electric power source to melt a single electrode and wherein the single electrode clamping means can be easily interchanged with a clamping means for bifilar electrodes by which a pair of electrodes can be melted by the same furnace installation. In conjunction with these objects, are further objects residing in the provision of a specific single electrode power operated clamping assembly using tongs, shoes and cooled electrical connections and of a specific bifilar electrode clamping assembly with hand operated clamping mechanism.

The crucible assembly used for the solidification of the ingot formed from the melting consumable electrodes can be generally of the form described and claimed in US. Pat. application Ser. No. 12,601, filed Feb. 12, 1970 to BE. Paton, et al., for System and Method of Electroslag Remelting of Metals and Alloys. The crucible described therein consists mainly ofa vertically disposed hollow crucible body with a coolant fluid jacket around the sides in order to cool the ingot formed by the melted consumable electrodes. The crucible body rests on and is supported by a fluid cooled bottom plate which is in turn mounted on a dolly enabling the crucible to be rolled into and away from melting position beneath the depending electrode(s).

The crucible assembly can be provided with a bottom pouring device by which molten slag can be rapidly introduced directly into the bottom of the crucible to effect a trouble-free and reproducible start-up of the remelting operation. The bottom pouring device can be of the type described and claimed in US. Pat. application Ser. Nos. 68,661 and 68,637, (now US. Pat. No. 3,670,089) both of which were filed Sept. 1, 1970 to B. E. Paton, et al., on Slag Introduction Method for Electroslag Remelting of Metals and Molten Slag Introduc tion Apparatus for Electroslag Remelting of Metals, respectively. The molten slag, which can be bottom poured into the crucible assembly through the bottom pouring device, functions to allow a smooth electrical start by reason of the slag being electrically conductive in the molten ionic state in which it is bottom poured. As the slag bath rises toward the previously electrified electrode(s) no current flows in the electric power circuit. However, at the instant when the electrically conductive molten slag engages the bottom end(s) of the electrode(s) the electrical circuit is completed, current starts to flow and the remelting operation commences.

Crucibles with the bottom pouring device are usable without modification for both the single electrode melting mode and the bifilar electrode melting mode.

If desired, the furnace operations can be started without use of the bottom pouring device. One method of start-up is to pour molten slag into the top of the crucible prior to the time that it is moved under the electrodes and to then immediately move it into place, positioned under the electrodes, move the electrodes down into the molten slag and turn the electric power on. As another alternate method, the molten slag can be carefully poured in the crucible from the top while the electrodes are in position, care being taken not to splash molten slag onto the electrodes which could then freeze on the electrodes and form pieces of solidified flux known as slag sows which thereafter fall into the molten metal bath and create electrical disturbances which cause imperfections in the ingot being formed.

Another method of start-up without the use of the bottom pouring device is known as a dry start in which metal turnings and an exothermic slag mixture are placed in the bottom of the crucible and particulate flux is poured into the crucible from the top with the electrode(s) in place. The power is then turned on and initial current flow from the electrodes initiates igniting of the exothermic slag mixture which completes burning to burn and melt the metal turnings, and at the same time melt the particulate flux into a molten slag bath which then provides the current path. In order to prevent burnout of the crucible bottom plate when this dry start method is practiced, a large protective dummy plate must be secured in the bottom plate of the installation. Such a dry start can he usually effected if a large dummy plate or striker plate is integrally secured to a stub portion which is retained within the bottom plate structure such as illustrated in FIG. 7 of above-mentioned US. Pat. application Ser. No. 12,601. This dummy plate can then be provided with an upstanding steel border for retaining a pile of metal chips onto which is placed an exothermic slag and the particulate flux. The electrode(s) is lowered onto this mixture and then an additional amount of the particulate flux is added around the positioned electrode. The electric power is turned on, the circuit is completed by the metal chips and an arc is struck which initiates burning and melting the exothermic flux. As that flux becomes molten the particulate flux penetrates between the striker plate and the electrode and becomes molten. It is necessary to then raise the electrode(s) slowly in order to allow more particulate flux to become molten until the point when all of the flux is molten. The electrode(s) is then positioned above the remainder of the dummy plate for continuation of the melting operation. In this dry start-up method the exothermic flux mixture can consist of the following: 17 percent of a 50-50 percent mixture of aluminum and magnesium turnings, 17 percent potassium nitrate, and 66 percent calcium difluoride. As a general rule, such dry starts are more effective in single electrode furnaces than in multiple electrode furnaces.

Therefore, in accord with the foregoing discussion, various ways of initiating furnace operation are contemplated and possible in the convertible furnace and in particular it is another object of the present invention is to provide for a bottom pouring device on the crucible assembly used in the convertible furnace in order to provide for a reproducible smooth start-up of the melting operations for both the single electrode melting mode and the bifilar electrode melting modes.

Further novel features and other objects of this invention will become apparent from the following detailed description, discussion and the appended claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS Preferred structural embodiments of this invention are disclosed in the accompanying drawings, in which:

FIG. I on two sheets as FIGS. 1A and 1B, is a side elevation view of the convertible electric furnace structure according to the present invention, assembled for operation in a bifilar electrode mode;

FIG. 2 is a front vertical view of the upper portion of the furnace assembly shown in FIG. 1;

FIG. 3 is a horizontal section view, taken on line 3 3 of FIG. 2, showing details of the dual or bifilar electrode clamping assembly and its coupling to the upper tower carriage;

FIG. 4 is a side elevation view of the top portion of the same basic furnace structure shown in FIG. 1 but in accord with the present invention is shown with the alternate single electrode clamping assembly coupled to the uppertower carriage;

FIG. 5 is a top view of the furnace in the single electrode mode as shown in FIG. 4;

FIG. 6 is a horizontal sectional view, taken along line 6-6 in FIG. 4, showing details of the operating mechanism of the single electrode clamping assembly;

FIG. 7 is a vertical sectional view, taken alone line 77 of FIG. 6 showing further details of the single electrode clamping assembly;

FIG. 8 is a vertical sectional view, taken along line 88 of FIG. 4, showing the details of the electrode shoes in cooperation with the gripping portions of the electrode clamping tongs.

DESCRIPTION The initial part of this description will describe the furnace construction illustrated in FIGS. 1-3. While that construction shows the bifilar consumable electrode melting mode, the illustrated basic furnace components are the same as those seen in FIGS. 4-8 which show the single electrode melting mode. Accordingly, the initial part of this description will be directed primarily toward the basic furnace components to which the same reference numerals will be applied in all Figures.

The furnace is best seen in FIG. 1 which is on two sheets as FIGS. 1A and 18. FIG. 1A shows the upper part of the furnace with the upper carriage and electrode clamp assembly, while FIG. 1B shows the lower part of the furnace with its lower carriage and the melting crucible assembly. Various details of the upper part of the furnace are also illustrated in FIGS. 2 and 3, to which reference will be made as necessary.

Referring more specifically to FIG. 1 (FIGS. 1A and 1B), the basic electric furnace installation 10 includes a vertical support tower 11, an upper carriage 12 and a lower carriage 13. The tower is hollow and cylindrical and the two carriages are mounted on the tower for controlled travel, up and down. The lower carriage releasably connects to and stabilizes a water cooled crucible 14. This is enabled by fork or yoke shaped support arms 15 on the carriage, the arms having end sockets which hook under two trunnions 16 rigidly affixed to the outer sidewall portions 17 of the crucible 14. The crucible assembly is supported on a dolly l8 equipped with rollers or wheels enabling movement of the crucible into and out of melting position.

Inasmuch as FIG. 1 shows the bifilar melting mode, the two electrodes 19 and 20, which can be positioned to depend down into crucible 14, are shown as vertically supported by an electrode clamping device 21 which, as will be hereinafter described in detail, is removably connected to the upper carriage 12. Connected to the electrode clamping device 21 are electric power conductors, one conductor 22 being shown in FIG. 1, which are also connected to a source of electrical power (not shown). The dolly l8 and a furnace tower base plate 23 rest on the floor 24 which is provided with a channel 25 aligned with the parallel vertical center axes of the furnace tower and the crucible 14. An endless cable 26 in channel 25, connects to a motor drive (not shown) and by a suitable connector to the dolly 18, moves the dolly with the crucible into and out of remelting position adjacent tower I1. Bracing gussets 27, as necessary can be welded between the base plate 23 and tower 11 for structural reinforcement.

Diametrically opposed front and rear vertical guide rails 28 and 29 extend the entire length of and are secured by suitable fastening means to tower 11. The lower carriage 13 has front grooved guide rollers, 30 and 31 embracing and guided for rolling along the front track 28; and rear guide rollers 32 and 33 for rolling along the rear rail 29. In a similar fashion, the upper carriage 12 has grooved front roller wheels 34 and 35 guided for rolling along front rail 28, and grooved rear roller wheels 36 and 37 guided for rolling along the rear rail 29. As illustrated, the rear rail 29 is a toothed rack, its teeth facing outward from the tower. The rack provides for drive cooperation to raise and lower the carriages by a power driven lower carriage sprocket wheel 38, shown in phantom lines, and a power driven upper carriage sprocket wheel 39, also shown in phantom lines. The drive power for sprocket wheels 38 and 39 is furnished by respective electric motors 40 and 41, attached by their motor housings to respective lower and upper carriages l3 and 12.

In FIG. 2, the top end of front rail 28 can be seen just under the U-shaped water coolant line 51 at the top of tower I1 and, below carriage 12, is shown extending downwardly along the front of the tower. The truncated wedge shape of rail 28 is clearly seen in FIG. 3, the base edges 101 and 102 being wider than the center surface 103. Reinforcement half circle bands 104 and 105 secured together, are secured around the lower end of upper carriage 12 and, in similar fashion, upper end reinforcement half circle bands 106 are provided. The reinforcement bands give upper carriage 12 greater structural stability where the front guide rollers 34 and 35 and the rear guide rollers 36 and 37 contact the front rail 28 and rear rail 29 respectively. Lower carriage 13 is provided with similar reinforcement bands.

Secured, as by welding, to the front portion of upper carriage 12 are two laterally projecting, heavy coupling brackets 42 and 43, apertured on a vertical axis to receive a removable coupling pin by which the different electrode clamping devices are secured to the upper carriage. The apertures in the two brackets are square for a purpose to become apparent as this description proceeds. The square coupling pin 44, shown in FIGS. 1 and 3, is a special component for the bifilar electrode clamping device 21 and, as is true of the clamping device 21, is not a basic furnace component. The tubular nature of the upper carriage 12 is shown in FIG. 3, and the carriage is maintained in concentric alignment relative to tower 11 by the guide rollers in contact with the front rail 28 and the rear railrack 29. The upper and lower, heavy support brackets 43 and 42, to which the bifilar electrode clamping device 21 as well as the single electrode clamping device to be hereinafter described, is coupled, are rigidly secured as by welding to the forward portion of carriage 12. Additional structural reinforcement can be provided as by the intermediate brace plate 119 provided in abutting contact and secured by welding to the bracket arms 42 and 43 and against the wall of upper carriage l2. Brackets 42 and 43 are made with vertical openings to retain the square cross-section pin 44 which is removably held by the respective brackets. The opening in at least the lower bracket 42 is square to match the square cross-section of pin 42 and to thereby non-rotatably locate and align the clamping device 21 when the square pin is inserted.

Rotatably mounted on the top of tower 11 are a pair of pulleys 53 enclosed in a cowling 54 which is removably supported on the upper end of the tower. The pulleys 53 guide a pair of cables, one such cable 55 being shown, which pass over the pulleys and down into the interior of the tower where they connect as by a suitable yoke device (not shown) to a cylindrical counterbalance 56 made from a group of disc shaped weights (shown in phantom lines) within the tower. Travel of the counterweight 56 up and down is guided by a central vertical guide post 57 inside and extending the length of the furnace tower. Guide post 57 is secured to the ends of the tower by conventional bracket structure (not shown).

The exterior ends of the two cables 55 pass from the top pair of pulleys 53, around respective ones of a lower pair of pulleys mounted on each side of the upper carriage 12, one such lower pulley 58 being shown. The exterior end of cable 55 is then rigidly connected to the sidewall of upper carriage 12 by means of a cable end eye member 59. The eye member 59 is fastened to a tie bolt 60 retained within an outer sleeve 61 which abuts a vertical base plate 62 which is rigidly affixed and extends from each side near the rear of the upper carriage 12. This particular direct connection to the carriage is used for the bifilar mode and is modified as will be hereinafter described for the single electrode mode. A pulley shield plate 63 is provided for each of the lower pulleys 58 in order to mount the pulleys in the correct transverse and aligned position with respect to the upper pair of pulleys. By such arrangement, the counterweight 56 is used to offset about one-half the combined weight of the upper carriage 12, the complete electrodes 19 and 20 and the electrode clamping device 21. Pulley wheels 58 are rotatably mounted within pulley shields 63 on axles 64, supported between the sidewall of the carriage l2 and the pulley shield plates 63.

Turning to FIG. 1B, the lower part of installation 10, the crucible 14 is provided with a bottom plate structure 65 which includes a bottom pouring device 66 for starting the furnace with molten slag as hereinbefore described.

Also provided on the bottom plate is a connection for an equalizing current bottom electrical power line 67 which is connected to a current conductor 68 and transmits electrical power from a power source, (not shown), in order to maintain equal electrode lengths for consumable bifilar electrodes 19 and 20. The electrical connections and the function for the current equalizing line are fully described in US. Pat. Application Ser. No. 676,873, filed Oct. 20, 1967 to B. E. Paton et al. for Multiple Electrode Electroslag Casting Having Current Equalizer. Bottom pouring device 66 has a wide-mouthed funnel 69 leading into an upright slag pouring channel member 70 which is supported on and is in fluid communication through the crucible-bottom plate assembly to provide for the flow of slag from funnel 69 directly into the interior of the crucible 14 without being top-poured. According to preferred procedure, before bottom pouring commences, electrodes l9 and 20 are positioned within crucible means 14 and are then connected to the electric power source. In bifilar operation using the equalizing current line 68, such line is also connected to the source prior to bottom pouring. With the power source energized, pouring of molten slag into funnel 69, through channel member 70 and into the remelting zone at the bottom portion of crucible 14 causes slag to engage the electrodes and starts current flow through the molten slag between the lower ends of the electrodes in order to further heat the slag bath. The electrical start occurs in a smooth, reproducible fashion from run to run, which allows commercial start-ups of the electroslag furnace to occur without the possibility of false starts.

The crucible bottom plate and bottom pouring structure 65 are supported by a base support structure 71 which rests on a vertical tilt adjustment means 72 supported on the bed 73 of dolly l8. Appropriate rails provide a track for the wheels 74 and 75 of dolly 18. Dolly 18 is adapted to be connected at its underside with the motive power cable 26 via a depending coupling member 76.

Appropriate water cooling ports 77, 78, 79 and 80 are provided on the bottom plate 65 and into the hollow crucible sidewalls 17 to circulate a cooling fluid such as water through the crucible and its bottom plate, for controlled cooling of the ingot being formed within the crucible.

To provide greater rigidity for the funnel 69 and its connected channel member 70, one or more reinforcement gussets 81 may be connected as by welding between member 70 and the top surface of bottom plate 65.

With plural electrodes, when current first starts to flow through the electrodes and the molten slag bath established within crucible 14, the resulting current surge sets up an electromagnetic field which provides a force tending to make the electrodes move apart. Such a movement can cause the electrodes to come into contact with the inside walls of the crucible if not properly controlled and this is particularly true where consumable electrodes of exceptionally long length are employed. To prevent that condition from occurring, a lateral electrode guide device 82 may be positioned and secured on the top end of the crucible. The electrode guide device includes insulated rollers (not shown) mounted to provide rolling contact with outermost surfaces of the two consumable electrodes 19 and 20, permitting vertical feeding of the electrodes yet preventing the electrodes from moving apart into contact with the crucible walls. Also provided at the top of crucible 14 is a gas collection and removal hood 83 (shown in phantom lines) which can be connected to a conventional gas draw-off apparatus.

As auxiliary equipment, a material discharge tube 84 leading from a hopper 85 via a variable particulate metering device 86 enables addition of deoxidizing compounds and/or particulate flux during the remelting operation. The hopper structure can be supported on a platform 87 mounted near or on the tower 11 in a fixed position with respect to the top of the crucible 14. If desired, the hopper support platform 87 may be made vertically adjustable to provide for different heights of crucibles.

The furnace operational sequence, in general, is similar for the single electrode mode and for the bifilar mode as will become apparent from the following operational sequence as described in conjunction with the bifilar mode shown assembled in FIGS. 1, 2 and 3.

Electrodes 19 and are lifted and placed in the electrode clamping device 21. Lifting is preferably done by a crane hoist which has a hook or a gripping mechanism which fastens to or grips an eye or lug bolt 88 generally welded on the upper end portion of each electrode. In practice, an electrode normally includes an upper electrode stub 89 to which is welded the consumable part of the electrode, as shown by weld line 90 on electrode 19 in FIG. 1. When electrodes are made in such a manner, the electrode stubs can be used repeatedly with different kinds and shapes of consumable bottom portions 19 and 20 and the electrode stubs do not have to be remelted.

When the electrode or electrodes have been placed in position relative to the clamping device, it or they are tightly clamped by the electrical contact shoes in the clamping device.

The upper carriage 12 is then lowered by its motor 41, driving through sprocket wheel 39 engaged with the fixed railrack 29, to position the lower ends of the electrodes to within a predetermined distance above the interior of the crucible bottom plate 65. When the proper electrode positioning has been attained, the electrical power source to the connecting lines 52 and 68 is then switched on and molten slag is poured into the funnel 69 from either a slag heating crucible or a ladle until there is an indication of current flow in the electrical power source circuit. This electrical flow commences the instant the electrically conducting molten slag bath reaches the lower ends of the electrodes. This procedure provides a smooth reproducible start-up for the melting operation, enabling achievement of a high melting productivity.

The melting operation is continued under the slag bath with crucible l4 maintained in fixed position and with electrode carriage 12 being lowered in a controlled fashion to maintain the lower ends of the electrodes at the proper position within the slag bath which will rise as the electrodes melt and the ingot is formed within the crucible. When the electrodes have melted completely to provide molten metal for the ingot, movement of upper carriage 12 is reversed and the remaining portions of the electrodes are raised away from crucible means 14. If desired, the bottom pouring device 66 can be removed prior to completion of the melting for an. ingot formation, the solidified flux cleaned out therefrom and the bottom pouring device installed on another crucible assembly being made ready for a subsequent remelting run.

After remelting is completed and the remaining portions of the electrode pairs 19 and 20 have been withdrawn from crucible means 14, the ingot is permitted to solidify within the mold. The crucible 14 is lifted up from its bottom plate to strip the crucible from the ingot. Lifting of lighter weight crucibles can be done by moving the lower carriage 13 upwardly along the tower 11 via its motor drive 40, upward movement of carriage 13 being imparted to the crucible sidewalls 17 through carriage arms 15 which are rigidly secured to the carriage on a bracket 91. The ends of the spaced apart carriage arms 15 have U-shaped socket members 92 which fit under and receive crucible sidewall trunnions 16. When heavy ingots and correspondingly heavy crucibles are involved stripping is best accomplished by a crane or equivalent lifting mechanism with rigging hooks or lifting arms engaging the trunnions 16 on the crucible sidewall.

solidification of the ingot occurs quite rapidly due to fluid coolant flowing within the sidewalls 17 of the crucible 14. By using additional dollys 18 and additional crucibles 14, extra mold units can be assembled ready to be moved into position by the dolly transporting cable 26 as desired. For the following remelting operation a second set of electrodes is inserted in the electrode clamping device 21. Following a procedure as just described, an efficient production cycle can be maintained to accomplish high productivity output from the described furnace installation.

BIFILAR ELECTRODE CLAMPING ASSEMBLY With reference to FIGS. 1, 2 and 3, the bifilar electrode clamping device 21 is a box-like structure with a frame fabricated from steel plates to form a bifurcated horizontal member 45 which also includes two forwardly disposed laterally spaced portions thereof which encompass the area in which the upper ends or stubs of the electrodes 19 and 20 are clamped. Enclosed within the front spaced portions of body 45 are two L-shaped electrode shoes 107 and 108. One leg of each of the L- shaped shoes face each other in coplanar position and are spaced apart by a plate or thin layer of high compression strength electrical insulation 109. The upper ends of the electrodes 19 and 20, fit within their respective electrode shoes and are clamped within the L of the shoes in a tight surface to surface electrical contact by means of the clamp bolts 47 and 110 for electrodes 20 and 19, respectively. Secondary safety clamping members 49 and 115, which include clamping bolts 113 and 131, can be swung into place about their pivot pins 112 and 130 affixed in the ends of the spaced front portions of the horizontal support member 45. Secondary clamp bolts 113 and 131 can either be screwed into engagement with the front face of respective electrodes 20 and 19 or they can be spring urged into contact with the electrode. Swinging movement of the two secondary clamping members 49 and 115 is limited by stop pins 114 and 116 secured in the front faces of the spaced portions of support member 45.

The open box structure 45 of the bifilar clamping device 21 has a heavy steel base plate 76 with two forwardly extending shelves at each side of the plate. Welded to the rear edge of the base plate 76 is a vertical back plate 123. The front vertical edges of two rectangular side plates 121 and 122 are welded to the back plate and extend in a converging manner to the rear of the box structure 45. The two converging side plates are joined at the rear edges by welding thereto, heavy upper and lower apertured coupling discs 120, and together with the discs provide a coupling by which the clamping device 21 is secured to the upper carriage 12. Both of the apertured discs 120 have square openings and they are spaced vertically to closely fit between the heavy support brackets 42 and 43 on upper carriage 12. The square pin 44 is then placed down through the aligned square holes in brackets 42 and 43 and in the coupling discs 120 to accurately align the clamping device 21 on the carriage 12 in front of the tower 1 1.

Best illustrated in FIG. 3, but also apparent in FIG. 1, short vertical sidewall plates 124 and 125 are welded to and extend forward from opposite ends of the back plate 123. Sidewalls 124 and 125 have openings 126 and 127 within which the clamping bolt assemblies 47 and 110 are mounted. Small front panel plates 128 and 129 are welded to the side plates 124 and 125 and provide support for the pins 112 and 130 of the secondary clamping means 49 and 115. If desired for safety, contact pin 113 of secondary clamping means 49 and corresponding contact pin 131 of secondary clamping means 115 can be arranged to spigot or screw into the front portions of the respective electrodes in order to prevent the electrodes from falling should the primary clamping means fail. This feature is important in a tight production schedule due to the fact that clamping bolts 47 and 110 might not be clamped sufficiently tight to hold the electrodes in place.

The internal surface of the open box shaped bifurcated front end of horizontal box support 45 is formed by a vertical plate 132 designated as an electrode support panel, spaced forward from rear vertical plate 123. Plate 132 is in turn connected to inner vertical sidewall plates 133 and 134 which are spaced inwardly from and are coplanar with the outer sidewall plates 124 and 125. Placed against the electrode support panel 132 surface as well as against portions of the inner sidewall panels 133 and 134 are sheets or layers of electrical insulation 135 which serve to insulate the L-shaped electrode contact shoes 107 and 108 from the box-like horizontal support 45. In a like manner, electrode engagement clamp elements 136 and 137, which are connected on the ends of respective clamping bolts 47 and 110, are electrically insulated from the bolts and from the remaining structural elements by cooperation with high compressive strength insulating spools 138 and 139, respectively. The electrode engaging elements 136 and 137 are spaced from the sidewall openings 126 and 127 through which bolts 47 and 110 and the bearings 142 and 143 pass, and thus are not in electrical contact with the box-like support 45. The two electrode engagement elements are retained in the bearing blocks 142 and 143 by retaining bolts 140 and 141, which pass through the insulating spools 138 and 139, respectively. The bearing blocks 142 and 143, in turn are rotatably connected to the ends of clamping bolts 47 and 110, respectively. These clamping bolts 47 and include handles 48 and 111 respectively, and are threaded through respective matched internal threads in collars 46 and 144 which are rigidly affixed by means of screws to the outer side wall plates 124 and 125. The clamp bolts and bearing blocks have sufficient travel to enable accommodation of square and rectangular cross-section electrodes within the two electrode clamping shoes 107 and 108.

As shown in FIG. 3, internal sleeves extending between vertical wall plates 124 and 133 and between plates and 134 form the clamp screw bearing openings 126 and 127.

The clamping assembly hand operated clamp bolts can be replaced by other mechanical clamping, for example, a hydraulic piston unit with a clamping element for engaging the electrode or electrodes to be retained.

Illustrated by the several sets of phantom lines representing electrodes 19 and 20, it is apparent that different sizes and cross-sectional shapes of electrodes can be employed in and clamped within the clamping device 21.

To the top of each electrode shoe 107 and 108 is secured, as by screws or welding, a respective connector block 50 and 96, which provide the means by which electrical power line connections are made to the electrode contact clamping shoes.

The relationship of the electrical connection elements of furnace installation 10 can be more fully understood by combined reference to FIGS. 1 and 2. The upper carriage 12 and associated electrode clamping device 21 are shown at the uppermost position on furnace tower 11 and two electrodes 19 and 20 are shown by phantom lines to better illustrate additional structure. At the rear of tower 11, the electrical power line 52 is shown attached to a connection plate 94 on upper carriage 12. Plate 94 includes a clamp 95 which receives and clamps one end of power conduit 22, which extends to the front of carriage 12 where the other end of conduit 22 is rigidly affixed to the electrode connector block 50 on electrode contact shoe 107. The block 50 is also connected via an electrically insulated water cooling line 51 to the second connector block 96 provided on electrode contact shoe 108 for supplying electrical power to the second electrode 19. The second connector block 96 is connected to a power conduit 97 which leads to the rear of carriage 12 where it in turn is connected to a clam affixed to the upper part of a connector plate 99 to which a second power cable 100 is connected. Cable 100 depends from the upper carriage 12 in a manner parallel with the aforedescribed cable 52. The electrical conduit and coolant lines, which have metallic sidewalls, conduct both a fluid coolant and electrical current. An exception is the electrically insulated water coolant line 51, between the electrode clamping shoe connector blocks 50 and 96, which must be insulated from one another. Coolant fluid is continuously supplied through electrical and coolant conduit 52 into conduit 22, thence into connector block 50, through coolant line 51 into connector block 96 and thence through conduit 97 into conduit 100. As shown in FIGS. 1 and 2, coolant connection lines 22 and 97 have a horizontal portion at the top of upper carriage 12, passing through respective electrical connector clamps 95 and 98 and bend downwardly to connect with coolant fluid source conduits (not shownA CLAM). Seen in FIG. 2 are the vertically disposed power lines 52 and 100 which pass from carriage 12 to the power source. The design of the electrical conduits disposes the two lines spaced close to and parallel with one another at all times. That arrangement reduces the inductance losses caused by the high current employed in these parallel lines.

Using the clamping device 21 for the bifilar electrode melting mode of furnace operation, after the electrodes are positioned within electrode clamping device 21, as was described hereinbefore, the clamp bolts 47 and 110 are manually turned by the hand operators 48 and 111 until each electrode is clamped securely within the electrode clamping device. When the stubs 89 of the electrodes are being placed into the electrode clamping device, secondary clamping means 49 and 115 are swung out of the way, relative to the fixed front of the box-like support 45. Also, when lowering the bifilar electrodes 19 and 20 into the crucible 14, it is necessary to separate the electrode roller guide support 82 which normally will tend to press the two electrodes towards one another.

CONVERSION TO SINGLE ELECTRODE MODE To convert the electric furnace installation from a plural or bifilar electrode mode as shown in FIGS. 1, 2 and 3, into a single electrode mode as shown in FIGS. 4-8 for melting one electrode at a time, the following changes are made in the basic furnace structure. The power supply is interrupted. If the crucible 14 is square,

it should be rearranged so it is placed on its bottom plate 65 insuch a manner that one of the corners of the crucible faces forward rather than having one of the sides face forward as when two electrodes are used in making an ingot with a rectilinear cross-section. The crucible, thus positioned, is moved into position adjacent tower 11 by means of a dolly 18 and cable 26 in the same manner as hereinbefore described.

Next, the clamp connections and 98 are loosened and power conduits 22 and 97 are disconnected and detached therefrom. The square cross-section pin 44, which has a flat retaining head, is removed from its coupling location between clamping device 21 and the upper carriage brackets 42 and 43. The entire plural electrode clamp device, 21, i.e., the bifurcated box-like horizontal support 45, with the shoes 107 and 108 is then lifted away from the tower, for example, through the use of an overhead crane, leaving the basic tower 11 with its two carriages 12 and 13.

A single electrode clamping device as shown in FIGS. 4-8 is then lifted and placed on the upper carriage 12. In lieu of the square coupling pin 44 used to couple clamping device 21 to the carriage, a cylindrical pin 151 is used to connect clamping device 150 to the carriage support brackets. Electric power lines, represented by line 152 in FIG. 4, are then connected to the aforedescribed clamps 95 and 98 providing dual lines for a common current path to the single retained electrode 153. The cylindrical pin 151 is dimensioned to fit within the square holes of upper carriage brackets 42 and 43 and has a flat retaining head portion 154 as can be seen in both FIGS. 4 and 5.

The single electrode clamping device 150, as mounted on upper carriage 12 includes scissoring electrode tongs consisting of two tong pieces 155 and 156 joined in a swivelled arrangement, as well as being mounted on brackets 42 and 43, by the cylindrical pin 151. Each of the respective electrode tongs 155 and 156 has a long arcuate operating lever 157 and 158, lever 157 being integral with a short lever, jaw member 159, and lever 158 being integral with a short lever,jaw member 160. Operation of the long operating levers inwardly and outwardly normal to the axis of tower 11 and about the axis of pin 151 provide substantial mechanical advantage to and will cause the short lever jaws 159 and 160 to move outwardly and inwardly in order to release or clamp an electrode (shown in phantom lines).

The respective clamping jaws 159 and 160 have vertically disposed V-shaped notches 161 and 162, enabling clamping the electrode by engaging opposed corners thereof. This arrangement accurately positions the electrode to coincide with the placement of the crucible 14, above described, for the single electrode melting operation. Note: the electrode clamping jaws 159 and 160 do not clamp the electrode directly, instead they hold electrodes shoes 163 and 164, respectively, which are shaped at their outer surfaces to conform with the inner surfaces of the electrode clamping jaws. The electrode shoes in turn engage and make electrical contact with the electrode, the shoes being provided with flat upper portions 165 and 166, respectively, (FIGS. 7 and 8) for supporting electrical connection plates 167 and 168. One connection plate 167 is connected on the end of conductor 152, while the other connection plate 168 is connected on the end of electrical conductor 170. The double single channel power conductor lines 152 and 170 are then connected to one electrical clamp 95 and supplied with power from line 52. The bottom connection 67, described in connection with FIGS. l-3, has its power line 68 connected first to depending plate 99 of the upper carriage 12, FIG. 2, and then to a principle voltage point on the electrical power source. Line 100 is, of course, previously removed to provide for this connection of line 68. Line 52 is connected to the opposite voltage point on the electrical power source.

A U-shaped fluid coolant transfer line 171 (FIG. 8) is provided between the electrical connections to plates 167 and 168. Since the two plates are at the same potential, coolant line 171 need not be electrically insulating although it is preferable to have it nonconducting. The electrical power lines are of the same form as hereinbefore described relative to FIGS. 1-3 wherein coolant fluid flows in the center of the conduits and the electrical power flows in the metal conduit sheaths which have appropriate electrical insulation on their outer surfaces.

The rear ends of the two electrode tong long operating levers 157 and 156 are connected, respectively, to pairs of links bars 172, 173 and link bars 186, 187 as seen in FIGS. 4, 5 and 6, the connection means being pins 174 and 188. The opposite ends of the pairs oflink bars are connected to eye-lugs 175 and 185 diametrically disposed on the exterior front end of a pneumatic cylinder 176. The cylinder 176 is supported on a vertically disposed plate 177 on upper carriage 12, as best shown in FIG. 6, through cooperation with the piston assembly which includes a piston support plate 178 bolted to plate 177. The plate 178 integrally carries a piston rod 179 which passes through a sealed front end cap 180 and a sealed rear end cap 181 on the cylinder 176. A piston 182 is axially secured on rod 179 and is disposed inside of the cylinder 176. A controlled source of air under pressure (not shown) is connected to rear cylinder port 183 and air can be exhausted through an exhaust port 184 provided on the front end cap of the cylinder, as the cylinder moves relative to the piston.

Integral with the eye-lugs 175 and 185 are supplemental eye-hole supports 175' and 185, respectively, to which tie rods 189 and 190 connect. These tie rods terminate in tie bolts 60 and 191, respectively and are integrally connected to pivotal connecting members 59, as hereinbefore described in conjunction with FIGS. l-3. The connecting members 59 are in turn connected to the pair of cables 55 which pass around lower pulley pair 58 and upper pulley pair 53 and are connected to the cylindrical, concentric, counterweight 56 shown in FIG. 6.

It will be appreciated that in interchanging the clamping device 150 for the single electrode operation in lieu of the bifilar clamping device 21, the entire electrode tong pair 156 and its connected pneumatic cylinder 176 may be moved as a unit upwardly and over the top of cowl 54 and connected to the upper carriage 12 by means of cylindrical pin 154, the two cooperating support plates 177 and 178 then being connected by a mechanical connection means, such as screws (not shown). The tie bolts 60 and 191 can be connected to the eye-hole support members 175 and 185, respectively, by removing them from the outer sleeve member 61 (for bolt 60) and corresponding bolt sleeve (not shown) for bolt 191. Once connection between the tie bolts and the eye-hole support members is made the counterweight 56 continuously urges cylinder 176 to its forwardmost position against piston support plate 178. This in turn forces operating levers 157 and 158 outwardly away from the tower 11 to thereby tightly grip the electrode between clamping jaws 159 and 160. When it is desired to release the gripped electrode, air under pressure is introduced through port 183 to move cylinder 176 rearwardly relative to piston 182, thus moving the operating levers 157 and 158 inwardly, whereby jaws 159 and 160 release the electrode. The air pressure supplied to port 183 must be sufficient to overcome the force exerted by counterweight 56 through the cables and tie bolts 60 and 191.

For most efficient use of the convertible furnace described herein the weights of the upper carriage, the two electrode clamping devices 21 and together with the weights of the electrodes to be held thereby should be substantially balanced so that their interchange does not necessitate placing additional annular elements onto the counterweight 56. However, that can be easily done by raising the weight within the furnace tower and removing the cowl 54.

As shown in FIG. 5, and as described hereinbefore, the electrode clamping device 150 has been shaped, in FIGS. 4 and- 5 to receive square cross-section electrodes. Of course, if desired, the electrode shoes can be shaped in such a manner as to efficiently clamp a circular electrode or some other cross-section shape of electrode. For example, FIG. 6 shows a configuration for clamping a circular electrode between the internal faces 192 and 193 of the electrode shoes within the curved clamping jaws 159 and 160. Of course, a pair of electrode shoes could be provided with the same or different internal configuration on both the outside and the inside in order to fit a common jaw configuration, yet be enabled to grasp circular or square electrodes, as required.

Clamping jaws 159 and are made with a vertical generally arcuate shaped jaw portion 194 and 195, as best shown in FIG. 6, which terminates in a wedgeshaped tongue 196, 197. Each jaw also has agenerally horizontally disposed reinforcement flange 198, 198', which adds structural strength to the jaw portions. The electrode tong operating levers 157 and 158 also have outer and inner strengthening ribs 199 and 200.

FIG. 7 shows details of the electrode shoe 164 with its upper plate 166 situated above the electrode contacting or clamping surfaces 202. The shoe has a crosssection with the configuration shown in FIG. 6. Upper plate 166 is connected to electrical contact plate 168, as by bolts, and plate 168 in turn is connected to the power conductor and water coolant line 171. Jaw portion seen in side elevation, is swivelly mounted on the connecting pin 151 and is centered between the apertured fork connection arms 203 and 204 which form the swivel connection for the other tong operator arm 158.

The heavy apertured upper and lower support brackets 43 and 42, welded on the front of carriage 12 are shown in section and illustrate the close but free guided fit of the tong swivel joint between the brackets. This view also shows the stacked annular counterweight discs which, together, constitute counterweight 56.

FIG. 8, which is a section through the jaws and electrode shoes 163' and 164, shows how the jaw portions 194 and 195 fit into recesses in the shoes and thereby releasably couple to the shoes, enabling easy removal and replacement. Between the adjacent surfaces of trode 20' shown in phantom lines.

The invention may be embodied in other specific forms without departing from the scope, spirit, or essential characteristics thereof. Present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope and spirit of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is: I

l. A convertible electric furnace system for melting of consumable electrodes using either one electrode at a time or using plural electrodes which are simultaneously melted comprising: a furnace support means; an electrode clamping means, which can be either ofa single electrode clamping means or a plural electrode clamping means; a mounting means on said furnace support which is common structure to the mounting of each of the electrode clamping means; means securing said electrode clamping means on said mounting means and including cooperating members on the secured electrode clamping means and on said mounting means and a selectively releasable means which couples said cooperating members together; said securing means enabling selective interchanging of single electrode clamping means and plural electrode clamping means on said furnace support means via the mounting means, so that the furnace installation is readily changeable between a single electrode furnace installation and a plural electrode furnace installation; and crucible connecting means adapted to engage and stabilize crucible means for cooperation with a single electrode and for cooperation with at least two electrodes.

2. A convertible electric furnace installation as defined in claim 1, wherein said mounting means includes a connection means adapted to alternately connect to and support each of the referred to electrode clamping means through at least one conversion coupling means.

3. A convertible electric furnace installation as defined in claim 1, wherein said crucible connecting means includes at least one crucible trunnion support arm unit enabling alternate connection to a first crucible means for a single electrode melting operation, and to a second crucible means for a plural electrode melting operation.

4. A convertible electric furnace installation as defined in claim 1, wherein said furnace support means includes a fixed vertical structure and said mounting means comprises a carriage means mounted for vertical shifting movement on said fixed vertical structure, said carriage means including connection means rigidly secured thereto and adapted to alternately connect to and support each of the referred to electrode clamping means.

5. A convertible electric furnace installation as defined in claim 4, wherein at least two electric power line terminal connections are secured on said carriage means, and said terminal connections include releasable clamp means enabling electrical power line connections between said carriage means and alternately to a single electrode clamping means and a plural electrode clamping means.

6. A convertible electric furnace installation as defined in claim 5, wherein means on said carriage means enable fluid communication of coolant fluid into the electrical power line connections.

7. A convertible electric furnace installation as defined in claim 4, wherein a weight, cable and pulley system is included in said furnace support and is connected between said fixed vertical structure and said carriage means to provide a counterbalance force applied to said carriage means.

8. A convertible electric furnace installation as defined in claim 4, wherein said carriage means includes bracket means enabling attachment of a power driven operator for an electrode clamping means.

9. A convertible electric furnace installation as defined in claim 8, wherein said fixed vertical structure is a tower with vertical exterior tracks, said carriage means is mounted on said tower for rolling guided movement on said tracks with said connection means disposed on the opposite side of said tower from said bracket means.

10. A convertible electric furnace installation as defined in claim 9, wherein drive means are provided on said carriage means in engagement with said fixed vertical structure for moving said carriage means up and down along said tower.

11. A convertible electric furnace installation as defined in claim 1, wherein means are provided for supporting and laterally moving a crucible means into operational location adjacent said furnace support structure.

12. A convertible electric furnace installation as defined in claim 11, wherein said means for supporting and laterally moving the crucible means is a wheeled dolly and dolly support tracks leading to a location closely adjacent the base of said furnace support 7 means.

13. A convertible electric furnace installation as defined in claim 12, wherein drive means are provided for releasable connection with said dolly.

14. A convertible electric furnace installation as defined in claim 1, wherein said releasable means securing said electrode clamping means to said mounting means comprises a conversion coupling means.

15. A convertible electric furnace installation as defined in claim 14, wherein said conversion coupling means is a coupling pin; said means securing said electrode clamping means and said mounting means includes interleaved apertured members, a portion of which are integral with said electrode clamping means and a portion of which are integral with said mounting means, the apertures therein being aligned and receiving said coupling pin.

16. A convertible electric furnace installation as defined in claim 1, further including: a cooled crucible means engaged with said crucible connecting means; and means included in said furnace support means enabling controlled relative vertical movement of said electrode clamping means and said cooled crucible means.

17. A convertible electric furnace installation as defined in claim 16, wherein said cooled crucible means has a bottom support device enabling adjustment of vertical alignment of said crucible means with electrode means held in said electrode clamping means.

18. A convertible electric furnace installation as defined in claim 16, wherein said cooled crucible means includes a bottom pouring device enabling introduction of molten slag into the bottom portion of said crucible means.

19. A convertible electric furnace installation as defined in claim 18, wherein said bottom pouring device includes a crucible bottom plate, a substantially vertical channel member mounted on said bottom plate and a molten slag receiving funnel on said channel member, said bottom plate including means enabling fluid communication from said channel member to the interior of said cooled crucible means.

20. A convertible electric furnace installation as defined in claim 16, wherein said cooled crucible means includes a bottom plate, a dummy starting plate means is secured on said bottom plate and means are provided for said dummy plate means to receive an exothermic dry start material and enable a current path from said crucible bottom plate through said dummy plate means to an electrode held in said electrode clamping means and introduced into said material to initiate an exothermic dry start.

21. A convertible electric furnace installation as.

defined in claim 1, wherein said crucible connecting means include at least one crucible trunnion support arm unit enabling alternate connection to a first crucible means for a single electrode melting operation and to a second crucible means for a plural electrode melting operation.

22. A convertible electric furnace installation as defined in claim I, wherein said furnace support means includes a fixed vertical structure and said mounting means comprises a carriage means mounted for vertical shifting movement on said fixed vertical structure, said carriage means including connection means rigidly secured thereto and adapted to connect to and support said electrode clamping means selected from any of the referred to electrode clamping means.

23. A convertible electric furnace installation as defined in claim 22, wherein at least two electric power line terminal connections are secured on said carriage means, said terminal connections include releasable clamp means and electrical power line connections are provided from said clamp means to said carriage means for connection to consumable electrode means to be clamped in said electrode clamping means.

24. A convertible electric furnace installation as defined in claim 23, wherein means on said carriage provide fluid communication for coolant fluid into the electrical power line connections.

25. A convertible electric furnace installation as defined in claim 22, wherein said fixed vertical structure is a tower with vertical exterior tracks and means on said carriage means mounts said carriage means for guided movement on said tracks.

26. A convertible electric furnace installation as defined in claim 22, wherein drive means are provided on said carriage means in engagement with said fixed vertical structure for moving said carriage means up and down along said tower.

27. A convertible electric furnace installation as defined in claim 21, wherein means are provided for supporting and laterally moving a crucible means into operational location adjacent said furnace support structure.

28. A convertible electric furnace installation as defined in claim 22, further including: a cooled crucible means selected to match the type of electrode clamping means'secured to said carriage means, said cooled crucible means being engaged with said crucible connecting means; and means included in said furnace support means enabling controlled relative vertical movement of said cooled crucible means.

29. A convertible electric furnace installation as defined in claim 28, wherein said cooled crucible means includes a bottom pouring device enabling introduction of molten slag into the bottom portion of said crucible means.

30. A convertible electric furnace installation as defined in claim 29, wherein said bottom pouring device includes a crucible bottom plate, a substantially vertical channel member mounted on said bottom plate and a molten slag receiving funnel on said channel member, said bottom plate including means enabling fluid communication from said channel member to the interior of said cooled crucible means.

31. A convertible electric furnace installation as defined in claim 28, wherein said cooled crucible means includes a bottom plate, a dummy starting plate means is secured on said bottom plate and means are provided for said dummy plate means to receive an exothermic dry start material and enable a current path from said crucible bottom plate through said dummy plate through said dummy plate means to an electrode held in said electrode clamping means and introduced into said material to initiate an exothermic dry start.

32. A convertible electric furnace installation as defined in claim 22, wherein said carriage means includes bracket means, a power driven operator for said electrode clamping means is secured to said bracket means, and linkage interconnects said operator and said electrode clamping means.

33. A convertible electric furnace installation as defined in claim 32, wherein said fixed vertical structure is a tower with vertical exterior tracks, said carriage means is mounted on said tower for rolling guided movement on said tracks with said connection means disposed on the opposite side of said tower from said bracket means.

34. A convertible electric furnace installation as defined by claim 22, wherein said electrode clamping means consists of a pair of electrode clamping tongs and said means securing said clamping means to said mounting means, pivotally secures said tongs to said carriage means.

35. A convertible electric furnace installation as defined in claim 34, wherein a weight, cable and pulley system is included between said fixed vertical structure and said carriage means to provide a counterbalance force applied to said carriage means; and said cable is connected to said clamping tongs whereby said counterbalancing forces urge said clamping tongs into clamping engagement with an electrode.

36. An electric furnace installation as defined by claim 35, wherein a fluid motor is provided as a clamping means operator and is drive connected to said pair of electrode clamping tongs to urge said tongs away from clamping engagement with an electrode, said fluid motor being secured to said carriage means and including a fluid cylinder pivotally attached to operating levers on said pair of tongs.

37. A convertible electric furnace installation as defined in claim 36, wherein said carriage means includes bracket means and said fluid motor is secured on said bracket means.

38. A convertible electric furnace installation as defined in claim 37, wherein said fixed vertical structure is a tower with vertical exterior tracks, said carriage means is mounted on said tower for rolling guided movement on said tracks with said connection means disposed on the opposite side of said tower from said motor mounting bracket means.

39. A convertible electric furnace installation as defined by claim 32, wherein a drive motor is secured on said carriage means and includes a shiftable member drive connected to said pair of electrode clamping tongs to pivotally operate said tongs.

40. A convertible electric furnace installation as defined in claim 34, wherein electrode clamping shoes are retained in said clamping tongs, at least two electric power line terminal connections are secured on said carriage means, said terminal connections include releasable clamp means and electrical power line connections are provided from said clamp means to said carriage means and connect to said electrode clamping shoes; and insulating means insulate said shoes from said clamping means.

41. A convertible electric furnace installation as defined in claim 40, wherein means on said carriage means provide fluid communication for coolant fluid into the electrical power line connections.

42. A convertible electric furnace installation as defined in claim 34, further including: a cooled crucible means selected to match the type of electrode clamping means secured to said carriage means, said cooled crucible means being engaged with said crucible connecting means; and means included in said furnace support means enabling controlled relative vertical movement of said electrode clamping means and said cooled crucible means.

43. A convertible electric furnace installation as defined in claim 42, wherein said cooled crucible means include a bottom pouring device enabling introduction of molten slag into the bottom portion of said crucible means. I

44. A convertible electric furnace installation as defined in claim 43, wherein said bottom pouring device includes a crucible bottom plate, a substantially vertical channel member mounted on said bottom plate and a molten slag receiving funnel and said channel member, said bottom plate including means enabling fluid communication from said channel member to the interior of said cooled crucible means.

45. A convertible electric furnace installation as defined in claim 42, wherein said cooled crucible means includes a bottom plate, a dummy starting plate means is secured on said bottom plate and means are provided for said dummy plate means to receive an exothermic dry start material and enable a current path from said crucible bottom plate through said dummy plate means to an electrode held in said electrode clamping means and introduced into said material to initiate an exothermic dry start.

46. A convertible electric furnace installation as defined in claim 22, wherein said electrode clamping means comprises at least two electrode support and clamping units for clamping at least two electrodes.

47. A convertible electric furnace installation as defined in claim 46, wherein said electrode support and clamping units are complementarily opposed to one another with the clamping portions thereof disposed facing away from said carriage means.

48.'A convertible electric furnace installation as defined by claim 46, wherein each of said electrode support and clamping units has associated therewith secondary clamping means to clamp the electrode held by each of said units in a direction normal to the main clamping action of said electrode support and clamping unit.

49. A convertible electric furnace installation as defined by claim 46, wherein each of said electrode support and clamping means holds a single electrode by means of a screw clamping device which has a rotary operator attached to the outer end thereof.

50. A convertible electric furnace installation as defined in claim 46, wherein electrode clamping shoes are retained in said clamping units, at least two electric power line terminal connections are secured on said carriage means, said terminal connections include releasable clamp means and electrical power line connections are provided from said clamp means to said carriage means and connect to said electrode clamping shoes; and insulating means insulated said shoes from said clamping means.

51. A convertible electric furnace installation as defined in claim 50, wherein means on said carriage means provide fluid communication for coolant fluid into the electrical power line connections.

52. A convertible electric furnace installation as defined in claim 46, further including: a cooled crucible means selected to match the type of electrode clamping means secured to said carriage means, said cooled crucible means being engaged with said crucible connecting means; and means included in said furnace support means enabling controlled relative vertical movement of said electrode clamping means and said cooled crucible means.

53. A convertible electric furnace installation as defined in claim 52, wherein said cooled crucible means includes a bottom pouring device enabling introductions of molten slag into the bottom portion of said crucible means.

54. A convertible electric furnace installation as defined in claim 53, wherein said bottom pouring device includes a crucible bottom plate, a substantially vertical channel member mounted on said bottom plate and a molten slag receiving funnel on said channel member, said bottom plate including means enabling fluid communication from said channel member to the interior of said cooled crucible means.

55. A convertible electric furnace installation as defined in claim 52, wherein said cooled crucible means includes a bottom plate, a dummy starting plate means is secured on said bottom plate and means are provided for said dummy plate means to receive an ex othermic dry start material and enable a current path from said crucible bottom plate through said dummy plate means to an electrode held in said electrode clamping means and introduced into said material to initiate an exothermic dry start.

56. A convertible electric furnace system for melting of consumable electrodes using either one electrode at a time or using plural electrodes which are simultaneously melted comprising: a furnace support means; electrode clamping means, including single electrode clamping means used when the system is operated with a single electrode and plural electrode clamping means used when the system is operated with plural electrodes; a mounting means on said furnace support means which is common structure to the mounting of each of the electrode clamping means; means for securing an electrode clamping means on said mounting means and including cooperating members on the secured electrode clamping means and on said mounting means and a selectively releasable means which couples said cooperating members together; said securing means enabling selective interchanging of single electrode clamping means and plural electrode clamping means on said furnace support means via the mounting means, so that the furnace installation is readily changeable between a single electrode furnace installation and a plural electrode furnace installation; and crucible means for cooperation with a single electrode and for cooperation with at least two electrodes.

57. A convertible electric furnace system for melting of consumable electrodes using either one electrode at a time or using plural electrodes which are simultaneously melted comprising: a furnace support means; an electrode clamping means, for holding a single electrode; mounting means on said furnace support means for mounting said electrode clamping means; means securing said said electrode clamping means on said mounting means and including cooperating members on the secured electrode clamping means and on said mounting means and a selectively releasable means which couples said cooperating members together; and means for converting the furnace installation from single electrode operation to plural electrode operation utilizing said mounting means, so that the furnace in stallation is alternatively usable as a single electrode furnace installation or a plural electrode furnace installation; and crucible means for cooperation with the electrodes.

58. A convertible electric furnace system for melting of consumable electrodes using either one electrode at a time or using plural electrodes which are simultaneously melted comprising: a furnace support means; an electrode clamping means, for holding plural electrodes simultaneously; mounting means on said furnace support means for mounting said electrode clamping means; means securing said electrode clamping means on said mounting means and including cooperating members on the secured electrode clamping means and on said mounting means and a selectively releasable means which couples said cooperating members together; and means for converting the furnace installation from plural electrode operation to single electrode operation utilizing said mounting means so that the furnace installation is alternatively usable as a plural electrode furnace installation or a single electrode furnace installation, and crucible means for cooperation with the electrodes. 

1. A convertible electric furnace system for melting of consumable electrodes using either one electrode at a time or using plural electrodes which are simultaneously melted comprising: a furnace support means; an electrode clamping means, which can be either of a single electrode clamping means or a plural electrode clamping means; a mounting means on said furnace support which is common structure to the mounting of each of the electrode clamping means; means securing said electrode clamping means on said mounting means and including cooperating members on the secured electrode clamping means and on said mounting means and a selectively releasable means which couples said cooperating members together; said securing means enabling selective interchanging of single electrode clamping means and plural electrode clamping means on said furnace support means via the mounting means, so that the furnace installation is readily changeable between a single electrode furnace installation and a plural electrode furnace installation; and crucible connecting means adapted to engage and stabilize crucible means for cooperation with a single electrode and for cooperation with at least two electrodes.
 2. A convertible electric furnace installation as defined in claim 1, wherein said mounting means includes a connection means adapted to alternately connect to and support each of the referred to electrode clamping means through at least one conversion coupling means.
 3. A convertible electric furnace installation as defined in claim 1, wherein said crucible connecting means includes at least one crucible trunnion support arm unit enabling alternate connection to a first crucible means for a single electrode melting operation, and to a second crucible means for a plural electrode melting operation.
 4. A convertible electric furnace installation as defined in claim 1, wherein said furnace support means includes a fixed vertical structure and said mounting means comprises a carriage means mounted for vertical shifting movement on said fixed vertical structure, said carriage means including connection means rigidly secured thereto and adapted to alternately connect to and support each of the referred to electrode clamping means.
 5. A convertible electric furnace installation as defined in claim 4, wherein at least two electric power line terminal connections are secured on said carriage means, and said terminal connections include releasable clamp means enabling electrical power line connections between said carriage means and alternately to a single electrode clamping means and a plural electrode clamping means.
 6. A convertible electric furnace installation as defined in claim 5, wherein means on said carriage means enable fluid communication of coolant fluid into the electrical power line connections.
 7. A convertible electric furnace installation as defined in claim 4, wherein a weight, cable and pulley system is included in said furnace support and is connected between said fixed vertical structure and said carriage means to provide a counterbalance force applied to said carriage means.
 8. A convertible electric furnace installation as defined in claim 4, wherein said carriage means includes bracket means enabling attachment of a power driven operator for an electrode clamping means.
 9. A convertible electric furnace Installation as defined in claim 8, wherein said fixed vertical structure is a tower with vertical exterior tracks, said carriage means is mounted on said tower for rolling guided movement on said tracks with said connection means disposed on the opposite side of said tower from said bracket means.
 10. A convertible electric furnace installation as defined in claim 9, wherein drive means are provided on said carriage means in engagement with said fixed vertical structure for moving said carriage means up and down along said tower.
 11. A convertible electric furnace installation as defined in claim 1, wherein means are provided for supporting and laterally moving a crucible means into operational location adjacent said furnace support structure.
 12. A convertible electric furnace installation as defined in claim 11, wherein said means for supporting and laterally moving the crucible means is a wheeled dolly and dolly support tracks leading to a location closely adjacent the base of said furnace support means.
 13. A convertible electric furnace installation as defined in claim 12, wherein drive means are provided for releasable connection with said dolly.
 14. A convertible electric furnace installation as defined in claim 1, wherein said releasable means securing said electrode clamping means to said mounting means comprises a conversion coupling means.
 15. A convertible electric furnace installation as defined in claim 14, wherein said conversion coupling means is a coupling pin; said means securing said electrode clamping means and said mounting means includes interleaved apertured members, a portion of which are integral with said electrode clamping means and a portion of which are integral with said mounting means, the apertures therein being aligned and receiving said coupling pin.
 16. A convertible electric furnace installation as defined in claim 1, further including: a cooled crucible means engaged with said crucible connecting means; and means included in said furnace support means enabling controlled relative vertical movement of said electrode clamping means and said cooled crucible means.
 17. A convertible electric furnace installation as defined in claim 16, wherein said cooled crucible means has a bottom support device enabling adjustment of vertical alignment of said crucible means with electrode means held in said electrode clamping means.
 18. A convertible electric furnace installation as defined in claim 16, wherein said cooled crucible means includes a bottom pouring device enabling introduction of molten slag into the bottom portion of said crucible means.
 19. A convertible electric furnace installation as defined in claim 18, wherein said bottom pouring device includes a crucible bottom plate, a substantially vertical channel member mounted on said bottom plate and a molten slag receiving funnel on said channel member, said bottom plate including means enabling fluid communication from said channel member to the interior of said cooled crucible means.
 20. A convertible electric furnace installation as defined in claim 16, wherein said cooled crucible means includes a bottom plate, a dummy starting plate means is secured on said bottom plate and means are provided for said dummy plate means to receive an exothermic dry start material and enable a current path from said crucible bottom plate through said dummy plate means to an electrode held in said electrode clamping means and introduced into said material to initiate an exothermic dry start.
 21. A convertible electric furnace installation as defined in claim 1, wherein said crucible connecting means include at least one crucible trunnion support arm unit enabling alternate connection to a first crucible means for a single electrode melting operation and to a second crucible means for a plural electrode melting operation.
 22. A convertible electric furnace installation as defined in claim 1, wherein said furnace support means includes a fixed vertical structure and saId mounting means comprises a carriage means mounted for vertical shifting movement on said fixed vertical structure, said carriage means including connection means rigidly secured thereto and adapted to connect to and support said electrode clamping means selected from any of the referred to electrode clamping means.
 23. A convertible electric furnace installation as defined in claim 22, wherein at least two electric power line terminal connections are secured on said carriage means, said terminal connections include releasable clamp means and electrical power line connections are provided from said clamp means to said carriage means for connection to consumable electrode means to be clamped in said electrode clamping means.
 24. A convertible electric furnace installation as defined in claim 23, wherein means on said carriage provide fluid communication for coolant fluid into the electrical power line connections.
 25. A convertible electric furnace installation as defined in claim 22, wherein said fixed vertical structure is a tower with vertical exterior tracks and means on said carriage means mounts said carriage means for guided movement on said tracks.
 26. A convertible electric furnace installation as defined in claim 22, wherein drive means are provided on said carriage means in engagement with said fixed vertical structure for moving said carriage means up and down along said tower.
 27. A convertible electric furnace installation as defined in claim 21, wherein means are provided for supporting and laterally moving a crucible means into operational location adjacent said furnace support structure.
 28. A convertible electric furnace installation as defined in claim 22, further including: a cooled crucible means selected to match the type of electrode clamping means secured to said carriage means, said cooled crucible means being engaged with said crucible connecting means; and means included in said furnace support means enabling controlled relative vertical movement of said cooled crucible means.
 29. A convertible electric furnace installation as defined in claim 28, wherein said cooled crucible means includes a bottom pouring device enabling introduction of molten slag into the bottom portion of said crucible means.
 30. A convertible electric furnace installation as defined in claim 29, wherein said bottom pouring device includes a crucible bottom plate, a substantially vertical channel member mounted on said bottom plate and a molten slag receiving funnel on said channel member, said bottom plate including means enabling fluid communication from said channel member to the interior of said cooled crucible means.
 31. A convertible electric furnace installation as defined in claim 28, wherein said cooled crucible means includes a bottom plate, a dummy starting plate means is secured on said bottom plate and means are provided for said dummy plate means to receive an exothermic dry start material and enable a current path from said crucible bottom plate through said dummy plate through said dummy plate means to an electrode held in said electrode clamping means and introduced into said material to initiate an exothermic dry start.
 32. A convertible electric furnace installation as defined in claim 22, wherein said carriage means includes bracket means, a power driven operator for said electrode clamping means is secured to said bracket means, and linkage interconnects said operator and said electrode clamping means.
 33. A convertible electric furnace installation as defined in claim 32, wherein said fixed vertical structure is a tower with vertical exterior tracks, said carriage means is mounted on said tower for rolling guided movement on said tracks with said connection means disposed on the opposite side of said tower from said bracket means.
 34. A convertible electric furnace installation as defined by claim 22, wherein said electrode clamping means consists of a pair of electrode clamping tongs and said means securing said clampIng means to said mounting means, pivotally secures said tongs to said carriage means.
 35. A convertible electric furnace installation as defined in claim 34, wherein a weight, cable and pulley system is included between said fixed vertical structure and said carriage means to provide a counterbalance force applied to said carriage means; and said cable is connected to said clamping tongs whereby said counterbalancing forces urge said clamping tongs into clamping engagement with an electrode.
 36. An electric furnace installation as defined by claim 35, wherein a fluid motor is provided as a clamping means operator and is drive connected to said pair of electrode clamping tongs to urge said tongs away from clamping engagement with an electrode, said fluid motor being secured to said carriage means and including a fluid cylinder pivotally attached to operating levers on said pair of tongs.
 37. A convertible electric furnace installation as defined in claim 36, wherein said carriage means includes bracket means and said fluid motor is secured on said bracket means.
 38. A convertible electric furnace installation as defined in claim 37, wherein said fixed vertical structure is a tower with vertical exterior tracks, said carriage means is mounted on said tower for rolling guided movement on said tracks with said connection means disposed on the opposite side of said tower from said motor mounting bracket means.
 39. A convertible electric furnace installation as defined by claim 32, wherein a drive motor is secured on said carriage means and includes a shiftable member drive connected to said pair of electrode clamping tongs to pivotally operate said tongs.
 40. A convertible electric furnace installation as defined in claim 34, wherein electrode clamping shoes are retained in said clamping tongs, at least two electric power line terminal connections are secured on said carriage means, said terminal connections include releasable clamp means and electrical power line connections are provided from said clamp means to said carriage means and connect to said electrode clamping shoes; and insulating means insulate said shoes from said clamping means.
 41. A convertible electric furnace installation as defined in claim 40, wherein means on said carriage means provide fluid communication for coolant fluid into the electrical power line connections.
 42. A convertible electric furnace installation as defined in claim 34, further including: a cooled crucible means selected to match the type of electrode clamping means secured to said carriage means, said cooled crucible means being engaged with said crucible connecting means; and means included in said furnace support means enabling controlled relative vertical movement of said electrode clamping means and said cooled crucible means.
 43. A convertible electric furnace installation as defined in claim 42, wherein said cooled crucible means include a bottom pouring device enabling introduction of molten slag into the bottom portion of said crucible means.
 44. A convertible electric furnace installation as defined in claim 43, wherein said bottom pouring device includes a crucible bottom plate, a substantially vertical channel member mounted on said bottom plate and a molten slag receiving funnel and said channel member, said bottom plate including means enabling fluid communication from said channel member to the interior of said cooled crucible means.
 45. A convertible electric furnace installation as defined in claim 42, wherein said cooled crucible means includes a bottom plate, a dummy starting plate means is secured on said bottom plate and means are provided for said dummy plate means to receive an exothermic dry start material and enable a current path from said crucible bottom plate through said dummy plate means to an electrode held in said electrode clamping means and introduced into said material to initiate an exothermic dry start.
 46. A convertible electric furnace installation as defined in claIm 22, wherein said electrode clamping means comprises at least two electrode support and clamping units for clamping at least two electrodes.
 47. A convertible electric furnace installation as defined in claim 46, wherein said electrode support and clamping units are complementarily opposed to one another with the clamping portions thereof disposed facing away from said carriage means.
 48. A convertible electric furnace installation as defined by claim 46, wherein each of said electrode support and clamping units has associated therewith secondary clamping means to clamp the electrode held by each of said units in a direction normal to the main clamping action of said electrode support and clamping unit.
 49. A convertible electric furnace installation as defined by claim 46, wherein each of said electrode support and clamping means holds a single electrode by means of a screw clamping device which has a rotary operator attached to the outer end thereof.
 50. A convertible electric furnace installation as defined in claim 46, wherein electrode clamping shoes are retained in said clamping units, at least two electric power line terminal connections are secured on said carriage means, said terminal connections include releasable clamp means and electrical power line connections are provided from said clamp means to said carriage means and connect to said electrode clamping shoes; and insulating means insulated said shoes from said clamping means.
 51. A convertible electric furnace installation as defined in claim 50, wherein means on said carriage means provide fluid communication for coolant fluid into the electrical power line connections.
 52. A convertible electric furnace installation as defined in claim 46, further including: a cooled crucible means selected to match the type of electrode clamping means secured to said carriage means, said cooled crucible means being engaged with said crucible connecting means; and means included in said furnace support means enabling controlled relative vertical movement of said electrode clamping means and said cooled crucible means.
 53. A convertible electric furnace installation as defined in claim 52, wherein said cooled crucible means includes a bottom pouring device enabling introductions of molten slag into the bottom portion of said crucible means.
 54. A convertible electric furnace installation as defined in claim 53, wherein said bottom pouring device includes a crucible bottom plate, a substantially vertical channel member mounted on said bottom plate and a molten slag receiving funnel on said channel member, said bottom plate including means enabling fluid communication from said channel member to the interior of said cooled crucible means.
 55. A convertible electric furnace installation as defined in claim 52, wherein said cooled crucible means includes a bottom plate, a dummy starting plate means is secured on said bottom plate and means are provided for said dummy plate means to receive an exothermic dry start material and enable a current path from said crucible bottom plate through said dummy plate means to an electrode held in said electrode clamping means and introduced into said material to initiate an exothermic dry start.
 56. A convertible electric furnace system for melting of consumable electrodes using either one electrode at a time or using plural electrodes which are simultaneously melted comprising: a furnace support means; electrode clamping means, including single electrode clamping means used when the system is operated with a single electrode and plural electrode clamping means used when the system is operated with plural electrodes; a mounting means on said furnace support means which is common structure to the mounting of each of the electrode clamping means; means for securing an electrode clamping means on said mounting means and including cooperating members on the secured electrode clamping means and on said mounting means and a selectively releasable means which couples said coOperating members together; said securing means enabling selective interchanging of single electrode clamping means and plural electrode clamping means on said furnace support means via the mounting means, so that the furnace installation is readily changeable between a single electrode furnace installation and a plural electrode furnace installation; and crucible means for cooperation with a single electrode and for cooperation with at least two electrodes.
 57. A convertible electric furnace system for melting of consumable electrodes using either one electrode at a time or using plural electrodes which are simultaneously melted comprising: a furnace support means; an electrode clamping means, for holding a single electrode; mounting means on said furnace support means for mounting said electrode clamping means; means securing said said electrode clamping means on said mounting means and including cooperating members on the secured electrode clamping means and on said mounting means and a selectively releasable means which couples said cooperating members together; and means for converting the furnace installation from single electrode operation to plural electrode operation utilizing said mounting means, so that the furnace installation is alternatively usable as a single electrode furnace installation or a plural electrode furnace installation; and crucible means for cooperation with the electrodes.
 58. A convertible electric furnace system for melting of consumable electrodes using either one electrode at a time or using plural electrodes which are simultaneously melted comprising: a furnace support means; an electrode clamping means, for holding plural electrodes simultaneously; mounting means on said furnace support means for mounting said electrode clamping means; means securing said electrode clamping means on said mounting means and including cooperating members on the secured electrode clamping means and on said mounting means and a selectively releasable means which couples said cooperating members together; and means for converting the furnace installation from plural electrode operation to single electrode operation utilizing said mounting means so that the furnace installation is alternatively usable as a plural electrode furnace installation or a single electrode furnace installation, and crucible means for cooperation with the electrodes. 